Finned tube construction



Sept. 19, 1939. F. J. SIBLEY 2,173,666

FINNED TUBE CONSTRUCTION Filed April 20, 1936 3 Sheets-Sheet l INVENTOR.

HOydJJ/Z/ey E i 5.

ATTORNEY.

Sept. 19, 1939. $|BLEY I 2,173,666

FINNED TU BE CONSTRUCTION Filed April 20', 1936 3 sheets-sheet 2 INVENTOR. HoydIWZ/ey amvw ATTORNEY.

F. J. SIBLEY,

FINNED TUBE cous'rnucnou Sept. 19, 1939.

3 Sheets-Sheet 3 Filed April 20, 1936 INVENTOIIQ. F/g/a J J/Z /ey ATTORNEY.

Patented Sept. 19, 1939 UNITED STATES PATENT OFFICE 3 Claims.

tube construction and more particularly to heat exchanging devices.

It is an object of my invention to provide an improved finned tube comprising an improved three-sided joint construction for securing the plates in spaced relation upon a tube for heat ex changing and other purposes with greater mechanical strength, and increased thermal efliciency while eliminating the necessity of utilizing auxiliary securing means or material.

Another object of my invention is to provide an improved fin .tube construction comprising pairs of thermal conducting tubes each having a groove cut around its outer surface for receiving and securing a set of apertured fin plates, each plate having tabs deformed on opposite sides of the plane of the plate to follow in the groove and abut the tabs on opposite sides.

It is also an object of my invention to-provide an improved finned tube' assembly for heat exchanging apparatus comprising a tube having a plurality of helical grooves for receiving a plural- .ity of sets of pre-formed fin plates having helical edged apertures in said grooves to provide a'plurality of separated sets of plates'spaced apart in substantially parallel relation and the plates of each set contacting continuously between the plates and the tube.

The invention itself, however, both as to its construction and as to the method of and.apparatus for assembling the same, together with additional objects and advantages thereof, will best be understood from the following description of specific embodiments, when read in conjunction with the accompanying drawings, where like reference characters are applied to similar parts throughout and in which:

Fig. 1 is a side elevational view of a fin plate pierced and cut to provide helical edged apertures for receiving four tubular conduits therethrough; Figs. 2 and 3 are sectional views on lines 2-! and 3-! thereof;

Fig. 4 is a side elevational view of a tube having] a helical groove for receiving and securing a set of fin plates thereon;

Fig. 5 is a similar view showing a tube provided with'a' plurality of spaced helical grooves for securing a plurality of separated sets of mutually engaging fin plates; I

Fig. 6 is a longitudinal sectional view showing 'a grooved tube provided with a leader clamped in the end preparatory to assembling the fin plates thereon;

Fig. '2 is elevation view showing how the fin plates are guided onto the grooved tube;

Fig. 8 is a side elevational view showing a device for rotating a. plurality of grooved tubes simultaneously for receiving the fin plates thereon;

Fig. 9 is a longitudinal sectional view showing (01. 257-262) My invention pertains to an improved finned how the grooved tube is expanded for firmly gripping the assembly fin plates;

Fig. 10 is anelevation view showing the as sembly of a set of continuously contacting fin plates clamped upon an expanded tube, a portion of which is broken away to show the contacting plate tabs;

Fig. 11 is a similar view showing a tube provided with a plurality of helical grooves support ing a plurality of continuously contacting sets of fin plates in spaced relation;

Fig. 12 is a side elevational view of a different embodiment of a fin plate comprising a helical edged aperture;

Fig. 17 is .a sectioned elevational view of an embodiment of the invention comprising a tube having annular grooves deformed by expansion and shrinkage to firmly grip and secure plates disposed thereon for constructing multiple disc cutters, electrical condensers and the like. Fig. 18 is a side elevational view of another embodiment of fin plate;

Fig. 19 is an end elevational view thereof, and Fig. 20. is a plan view showing a finned tube assembly made'in accordance with the invention. Referring more particularly to Figs. 1. 2 and 3 of the drawings, thefin plates I,"in accordance with one embodiment of my invention, comprises a A substantially rectangular piece of sheet metal which is provided with four circular apertures 3 for mounting on tubular members when the structure is assembled. The fin plate i is cut through by slits 5 extending between each oi the pairs of apertures 3 adjacent the opposite ends of the fin plate to provide flexible tabs or wings I and 9.. between the adjacent pairs of apertures. The aifiacent pairs of tabs I and 0 are bent outwardly from the surface plane of the plate I in opposite directions, one of the tabs 1 of each pair projecting to the right and the other tab 9 of each pair projectingto the left, as viewed in Fig. 2, thereby distorting the edges of the apertures 3 into a substantially helical or spiral curvature.

The opposite sides of the plate I are also distorted or off-set into displaced substantially parallel planes 6 and t to further distort the edges of the apertures 3 and the intermediate portion of the plate to provide ahelically edged aperture which will be a full circle in projection on a plane perpendicular to the axis of the tube to fit freely into and contact fully around. a'helical groove on a tube. This off-set arrangement is more clearly shown in Fig. 2, but is also indicated by the shaded portions in Big. 1. The apertures thus formed are alternately right and left handed and any desired number may be conveniently provided.

The distorted edges of the apertures 3 are also preferably provided with an annular margin III, as shown in Fig. 3, which is straightened substantially parallel to the displaced edges of the plate I. Since the annular margin Ill encircling the apertures will be substantially at right angles to the axis of the tube, onwhich it will be mounted, it will enter the groove in the tube very readily. Because of the helical or spiral slope of theedges of the apertures thus provided in the fin plates, the plates may be secured upon a helical grooved tube and the maximum contact area with the tube is obtained.

The fin plates I may be pre-formed by hand tools and may be made of various shapes and with apertures to accommodate various numbers and arrangements of the tubes as desired. For mass production, the plates may be pre-formed by automatic sheet metal working machinery, in any suitable manner, as by a punch press provided with a suitable die, as will be readily understood. In the first station the holes are preferably pierced, slightly smaller than the finished hole, and in the second station the cuts may be made between the holes and the plate tabs may be distorted and the holes shaved to the final size. Suitable automatic sheet metal working machinery is well known in the art and does not constitute any part of the applicant's invention.

Because it is only necessary to bend the fin plates I but slightly in accordance with my invention, it is possible to make them of a very hard sheet metal of high density and thermalconductivity as it comes from the rolling mills. These plates may be assembled with high pressure engagement to provide good thermal contact.

After the pre-formed fin plates I have been provided with apertures 3, the edges of which are of substantially helical conformation, they may .be conveniently and efficiently assembled upon a tube II which, as shown in Fig. 4, has a groove I3 formed, cut, or sawed in any convenient manner around its outer peripheraisurface. The groove I3 is preferably of substantially helical conformation either right or left handed. Such a tube may be made of any material which has a suitable modulus of elasticity to take sufilcient .permanent distortion to be expanded diametrically and shrunk axially, in accordance with my invention, for drawing the side walls of the grooves together to grip and hold the fin plates, in a manner to be subsequently set forth. The grooved tube II may be made of any suitable length for supporting the desired number of plates'for various applicationsand installations. For heat exchanging purposes the grooved tube II is made of a metal of good heat conductivity having high ductility. For example, half hard copper, aluminum, or soft steel are suitable for this purpose.

A portion of the outer surface of the tube adjacent each end thereof may be turned down to provide a smooth surface of smaller diameter whereon the ends of the tube may be conveniently connected, in any suitable manner, with the source of heating or cooling or other medium which is to be utilized therein. When it is desired to support a plurality of separate sets of mutually engaging fin'plates in spaced relation, the grooved tube II must be provided with a plurality of pered cam surface 33 for receiving the wedgehelical grooves, such as, I3 and I5 spaced thereon, as shown in Fig. 5 for example. It will be understood that more than two grooves may be thus provided in spaced relation on the tube.

For the purpose of assembling the aperturcd fin plates I upon a. grooved tube II, I provide a leader II which, as shown in Fig. 6, is secured in the end of the tube. For this purpose the leader comprises a guide neck I9 having a shallow helical thread 2| on its outer surface for guiding the fin plates toward a leader head 23. The guide neck I9 and its external thread 2i are of a diameter smaller than the diameter of the apertures 3 provided in the fin plates whereby the plates may be readily dropped onto it. The leader head 23 is of substantially larger diameter than the neck and it is provided with a deep helical groove 25 for receiving the fin plates from the guide neck I9. The inner diameter of the helical groove 25 on the leader head is substantinlly larger than the neck I9 and is suitable for continuously guiding the fin plates in adjacent relation into the helical groove I3 on the adjacent end of the grooved tube Ii.

In order to secure the leader I! upon the end of a tube I I, a shaft 21 extends freely through the leader and carries a tapered wedge 29 thereon for spreading a set of split fingers 3| which extend from and are integral with the head 23. For this purpose, two fingers 3| of semi-circular cross-section are sufficient and these are provided at the inner ends with a substantially talike head 29 on the end of the shaft. The shaft 21 is provided with external threads35 which cooperate with internal threads between the friction fingers 3| adjacent the leader head for drawing the wedge 29 toward the leader head 23. This spreads the friction fingers 3| apart in snug frictional engagement with the inner surface of the tube II, as shown in Fig. 6.

The outer end of the leader shaft is provided witha square shank 22 for receiving a suitable wrench or hand-wheel thereo It will be understood that any number of frictional fingers 3| may be provided for this purpose to provide snug engagement with the internal surfaces of tubes of different diameter, and the outer surfaces thereof may be smooth or roughened to provide suitable gripping engagement with the tubes.

When the leader is applied to the end of a tube, it is firmly secured therein by turning the shaft 21 to expand the fingers 3i for engaging the tube. The leader is so applied that the end of the large groove 25 in the leader head suitably connects with the end of the fine helical groove I3 in the tube wherein the fin plates are guided onto the tube. Leaders are provided with right or left handed threads to fit the right and left handed grooved tubes.

After the leaders have been properly installed on the ends of a suitable number of the tubes I I, which are arranged alternately with right and left handed grooves, the fin plates I are dropped on over the guide necks I9. By turning the tubes II simultaneously in alternate reverse directions, the leaders are rotated relative to the fin plates I which are thereby guided forward and enter the deep helical grooves 25 in the leader heads in adjacent relation. By continuing the rotation, the fin plates I are started into the helical grooves I3 of the tubes. The fin plates I, as shown in Fig. -1, are thus simultaneously guided upon four grooved tubes I I which extend through the four apertures 3 of the plates. The leaders IT are then removed from the tubes by turning the shafts 21 in the reverse direction.

For convenience in rotating the tubes II simultaneously, I provide the assembling device shown in Fig. 8, which comprises chucks 24 of asuitable size for receiving and gripping the lower ends of the grooved tubes The chucks 24 are rotatably supported on the upper ends of individual shafts 26 which are vertically journallcd in a base plate 28. The base plate 28 also supports a bearing bracket 30 which has depending lend legs 32 secured to the ends of the base plate 28 in any suitable manner- The shafts 26 rise vertically through the bracket 30 which comprises bearing meanstherefore.

' The shafts 26 carry gears 34 which mesh together. for rotating the shafts simultaneously in alternate reverse directions. For driving the shafts 26, a drive shaft 36 is similarly journalled in the base 28 and the bracket 30 and carries a suitable gear 38 intermeshing with the adjacent one of the series gears 34. The drive shaft 36 may be-turned manually, or by any suitable motive means such as the electric motor 40 conne'cted thereto through gears 42 or speed changing means.

The order in which these steps are performed is immaterial as the tubes may be first other suitable mounted vertically in the assembling device chucks 24 and the guides l1 thereafter installedin the upper ends of the tubes and the apertured fin plates dropped thereon.

After the set of helically apertured fin plates is assembled on the tubes, the guides are removed from the upper ends of the tubes II by turning their shafts-21 in the reverse direction. On the lower ends of the tubes, the chucks 24 are released and the fin tube assembly is removed. In this manner any desired number of plates may be simultaneously assembled uponany number of grooved tubes. 7

For gripping and securing the fin plates upon the grooved tubes, I collapse the grooves to pinch the plates therein after the plates have been assembled on the tubes. For this purpose,

I provide an expander which, as shown in Fig. 9,

comprises an elongated stem 4| for extension through the tube H which is to be expanded. An enlarged expander head 43 is provided on the end of the stem and it carries a substantially sharp shoulder 45 extending in annular conformation around the leading edge of the peripheral surface of the head. A series of friction'reducing guide rings 41, comprising ridges extendingcircumferentially around the outer surface, are spaced axially along the expander head. Also the portion of the stem 4| joining the expander head is provided with a plurality of axially spaced annular guide rings 49.

To expand the tube H, the expander stem 4| passes freely therethrough, as shown in Fig. 9. The expander head 43 is then drawn through the grooved tube for which purpose force may be applied in any suitable manner as by mechanical, pneumatic or hydraulic means as will be readily understood. As the expander .passes throu h the tube, the annular guide rings 41 and 49 on the stem and the expander head serve to reduce the frictional losses which would be obtained if flat contacting surfaces were pro-- vided. The shoulder 45, which is rather sharp, on'the leading edge of the expander head 43 packs or collapses the tube II in the weakest portions under the grooves l3 thereby shrinking the,

' plates.

,grooves are drawn together to pinch or squeeze the edges of the helical apertures of the fin plates mounted thereon, while the bottoms of the helical grooves are expanded diametrically into snug abutting engagement.

After the tubes II have been expanded, the assembly of a set of continuously contacting fin plates I is clamped together thereon, as shown more clearly in elevation in Fig. 10, where a portlon of the tube is broken away to show the mutually engaging relation provided between the The oppositely disposed plate tabs 1 and 9 abut the-tabs 9 and 7 respectively projecting from the plates on opposite sides and provide a continuous airflow engaging surface between the parallel offset portions 6 and 8 of the plates with sufficient irregularity to provide eddies for efiicient heat transfer. Such a of fin plates on oppositely grooved tubes is also shown in plan view in Fig. 20. The helical edged apertures provide continuous thermal coupling between the plates and the tube and provide a rigid support around the helical'groove from one end of the tube to the other. The fifth plates I are supported in axially spaced and substantially parallel relation on the tube.

When a pluralitycf sepa ated sets of spaced fin plates are to be supported each in continuous contacting relation, Iprovide a tube H such as that shown in Fig. which has a plurality of helical grooves l3 and I5 or more thereon. The preformed fin plates l are then assembled simultaneously in the separate grooves on the tube by means of aleader which is provided with a plurality of spaced helical grooves, in a manner similar to the operation of guiding plates upon a grooved tube as previously described. After the plates have been assembled in adjacent conta/cting relation along the helical grooves, the tubes are expanded and the side walls of the grooves are collapsed for snugly gripping the inner edges of the apertures of the plates in a snug three-sided joint, as previously set forth, to provide an efilcient thermal coupling and mechanical support.

It is also possible by a simplified arrangement to obtain a single helical edged aperture in a fin plate, as shown in Figs. 12, 13 and 14. In accordance with this embodiment of my invention, a fin plate 5| is providedwith a single circular aperture 53 and a slit 55 is out diametrically from one edge o the aperture about one radius distance toward one edge of the-plate. The adjacent flexible points 51 and 59 thus provided .are bent in opposite directions from the plane of the plate, as shown in, Fig. 13. The portion of the fin plate 5| on the side of the aperture opposite from the slit 5'l is deformed into two spaced and substantially parallel planes 60 and 62, as shown more clearly in Fig. 14. The edges of the aperture 53 are thus distorted to substantially helical or spiral co-Tiformati n. Along the edges completed assembly annular portions 64 are flattened or deformed 7;

back to positions substantially parallel to the main plane of the plate i whereby they are perpendicular to a supporting tube and freely enter its grooves. Although only a single aperture 53 is shown in the square plate 5i. the latter may be of elongated rectangular or other conformation to provide a plurality of such helically edged apertures to receive as many grooved tubes as desired.

Fin plates of this conformation are guided upon and into the helical grooves of tubes ll similarly to the fin plates previously described. Such an assembly of plates on an unexpanded tube is shown in the enlarged Fig. 15, and a rear view thereof is shown in Fig. 16. After the plates 5| have been assembled on the grooves, the side walls of the grooves are collapsed together to grip the edges of the plate apertures. This is accomplished by expanding the tube diametrically and shrinking it axially in the manner previously described whereby the side walls of the groove l3 grip the sidesof the edges of the apertures 53, and the plates 5| are firmly secured thereon in efllcient thermal coupled relation.

In accordance with another embodiment. the principle of my invention may be utilized for supporting a plurality of plates 63 such as disk cutting engagement with the inner edges of the disk apertures. When the tube 64 is then expanded. as previously described, the side walls of the grooves 65 are drawn together sufiiciently to grip the plates or disks 63 quite firmly on the sides of their apertures.

For installations requiring a large fin area and a great many tubes, fin plates 61 are advantageously made, as shown in Figs. 18 and 19, with the tube receiving apertures 3 arranged in adja-'- cent parallel rows. To provide a rigid and thermally efficient relation, the apertures 3 in each row are preferably staggered relative to the apertures in the adjacent rows for receiving tubes which are disposed in similar staggered relations.

Slits 5 are out between adjacent pairs of apertures 3, as in the first embodiment of fin plate, shown in Fig. 1. To make helically edged apertures, the adjacent pairs of plate tabs 1 and 9 thus provided are bent outwardly in opposite directions and the plate is distorted to provide parallel offset portions on opposite sides of the row of apertures. As shown, the offset portion of the fin plate between the rows of apertures 3 provides a continuous aligned surface 69. The portions ll of the plate above and below the rows of apertures are parallel to but offset from the intermediate portion, and they are in alignment with each other, as shown in Fig. 19. The plate tabs 1 of each row, whic are directed toward each other, are distorted to the left and the tabs 9 which are directed away from each other are bent to the left of the plate as shown in Fig. 19.

It will be seen that I have provided a simple and rugged fin tube construction, and method and apparatus for conveniently assembling -the same, whereby the fin plates may be supported upon a grooved tube. in spaced relation in a simple convenient manner which provides im proved mechanical strength and increased thermal efficiency while eliminating the necessity for auxiliary fastening accessories and operations.

Aside from the specific embodiment of the invention herein shown and described, =-it will be understood that various details of the construction may be altered or omitted without departing from the spirit and scope of the invention as disclosed and claimed, and that I do not desire to limit the invention to the exact constructions herein set forth.

I claim:

1. A finned tube construction comprising, a pair of thermal conductive tubes, a right-handed groove in the peripheral surface of one of said tubes, a left-handed groove in the peripheral surface of the other one of said tubes, a fin plate having a pair of spaced tube receiving apertures for passing said tubes in spaced relation therethrough, a slit in said plate between said pair of apertures to provide a pair of deformable tabs, and the tabs on opposite sides of the slit being deformed in opposite directions from the plane of the plate to distort the edges of the apertures to follow in the respective right and left-handed grooves in said tubes.

2. A finned tube construction comprising, a pair of thermal conductive tubes, a helical righthanded groove in the peripheral surface of one of said tubes, a helical left-handed groove in the peripheral surface of the other one of said tubes, a fin plate having a pair of spaced tube receiving apertures of a diameter'greater than the tubes for passing said tubes in spaced relation therethrough, a slit in said plate between said pair of apertures to provide a pair of deformable tabs, the tabs on opposite sides of said slit being deformed in opposite directions from the plane of the plate to distort the edges of the apertures to follow in the respective right and left handed helical grooves in the tubes, and, the intermediate portion of said fin plate being deformed for distorting the plate to fill a complete circle projected on a plane perpendicular to the axis of the tube and to provide the maximum length of thermal contact in said helical grooves.

3. A finned tube construction comprising, two thermal conductive tubes, a right-handed helical groove in the peripheral surface of one of said tubes, a left-handed helical groove in the peripheral surface of the other one of said tubes, a fin plate, a pair of tube receiving apertures spaced in said fin platefor passing said tubes in spaced relation therethrough, a slit cut in said plate between said apertures to provide a pair of deformable tabs, said tabs on oppositesides of said slit being deformed in opposite directions from the plane of said fin plate to distort the edges of said apertures to follow in the respective right and left-handedgrooves in said tubes, said grooves having side walls firmly gripping the side surfaces of the edges of the tube receiving apertures and said grooves having bottom walls firmly abutting the inner surfaces of the edges of said tube receiving apertures.

FLOYD J. SIBLEY. 

